The unintentional initiation (i.e., firing) of a pyrotechnic device (i.e., fireworks projectile) is a most unforgiving event. Frequently, pyrotechnicians are present, often resulting in personnel injury or death. Equally common is the proximity of the initiated device to other pyrotechnic devices, potentially resulting in an uncontrolled escalation of the initial unintended initiation event into widespread unintended initiation events, with attendant major losses and destruction. This so-called “chain-reaction” is the by-product of a single pyrotechnic device communicating with, and initiating, other adjacent pyrotechnic devices. Once initiated, this chain-reaction can proceed so rapidly as to result in an event sometimes described as a “mass detonation”.
Several recent chain-reaction events have been well documented and studied. While each studied event was unique, communication between adjacent pyrotechnic devices was a universal theme and, ultimately, the cause of the resulting destruction and personnel trauma. Simply stated, without the presence of initiation communication between the several pyrotechnic devices, the event might have been limited solely to the initiation of the first pyrotechnic device.
As an analogous concept, consider a burn test of a single pyrotechnic device. With certainty, the test burn will ultimately initiate the device. Now consider a burn test of multiple pyrotechnic devices, much as the industry does when evaluating packaging concepts. The initiation of the first pyrotechnic device produces two results: (i) as a consequence of initiating the primary device's lift charge, the resultant pressure wave attempts to disburse (i.e., spatially separate) the adjacent pyrotechnic devices; and (ii) as a consequence of the primary initiation's thermal output, some number of the secondary pyrotechnic devices will also be initiated.
It should be noted that the initiation of a pyrotechnic device generally means that both the lift charge and, as a consequence, the burst charge, will initiate. This is because, in contemporary pyrotechnic device construction, the initiation of the time fuse for the burst charge is tied to initiation of the lift charge. This is done either by (i) using initiation of the lift charge to initiate the time fuse of the burst charge (i.e., “bottom fused”), or (ii) using a short length of quickmatch to initiate the time fuse of the burst charge (i.e., “top fused”).
More particularly, and looking now at FIG. 1, where the pyrotechnic device is a bottom fused device, the “leader” directly ignites the lift charge, which in turn ignites the time fuse for the burst charge. Where the pyrotechnic device is a top fused device, the leader directly ignites both the lift charge and the time fuse for the burst charge. In FIG. 1, the bottom fused construction is characterized as “alt”.
It is believed that, in chain-reaction events, the initiation of the burst charge is the more serious consequence. This is because it is the by-products of a burst initiation (namely, multiple flaming pyrotechnic compositions, each having a duration of several seconds) which typically initiate adjacent pyrotechnic devices.